1. Field of the Invention
The invention relates to a hydraulic driving vehicle comprising a pair of front and rear transaxles incorporating respective hydraulic motors, supplied with hydraulic fluid through pipes from a pump unit separated from the transaxles.
2. Related Art
Conventionally, there is a well-known working vehicle having front and rear transaxles incorporating respective hydraulic motors, which are supplied with hydraulic fluid from a pump unit separated from the transaxles, as disclosed in U.S. Pat. No. 6,732,828. Pipes are interposed among the pump unit and the front and rear transaxles so as to form a hydraulic circuit for circulating hydraulic fluid between a hydraulic pump in the pump unit and the hydraulic motors in the transaxles.
Hydraulic fluid circulated in the hydraulic circuit is heated as much as its pressure loss. Therefore, a cooling fan is usually provided on a pump shaft of the hydraulic pump projecting outward from a casing of the pump unit so as to blow and cool the casing, thereby cooling the circulated hydraulic fluid.
However, the effect of cooling hydraulic fluid is insufficient because the cooling effect by the cooling fan is transmitted to the hydraulic fluid through the casing of the pump unit.
Further, conventionally, a reservoir tank is fluidly connected through a piping to the hydraulic circuit including the hydraulic pump and motors so as to absorb excessive hydraulic fluid. The problem of the reservoir tank is that the absorption of excessive fluid from any of the pump unit and transaxles interferes with flow of fluid through another of the pump unit and transaxles.